De novo cavernous malformation after radiosurgery for cerebellar arteriovenous malformation: A case report

Stereotactic radiosurgery, including gamma knife radiosurgery (GKS), can in rare cases result in de novo cavernous malformations (CMs). Here, we present a case of de novo CM induced by GKS following treatment of a cerebellar arteriovenous malformation (AVM). A 48-year-old woman was diagnosed with left unilateral Moyamoya disease. Conventional cerebral angiography also revealed an AVM in the left cerebellum. The patient underwent GKS using a 50% isodose of 15 Gy at the margin of the left cerebellar AVM. Magnetic resonance imaging (MRI) taken 3 years after GKS revealed small chronic hemorrhages with perilesional edema in the left cerebellum. Five years later, the lesions became aggravated, but were asymptomatic. Eight years following GKS, the patient was admitted complaining of headache and dizziness. Brain MRI revealed a 1.3cm hemosiderin deposit with an inner hyperintense nodular portion that was enhanced in the left cerebellum. An open craniotomy was performed and the mass was removed, from which pathological findings were compatible with those for CM. The patient recovered to the prehemorrhagic state. This case shows that De novo CMs can rarely develop after radiosurgery. Most CMs have been reported to develop following radiosurgery for brain tumors. As shown in this patient, CMs can also develop after radiosurgery for cerebellar AVM in adults.